These investigations are designed to study the mechanisms of somatic motor function in primates using morphological techniques. Autoradiographic methods for analyzing neural pathways will be used to study the efferent projections o the red nucleus and other nuclei involved in control of motor activity. Tritiated leucine will be injected into these nuclei using stereotactic methods. The Fink-Khimer method for demonstrating degenerating nerve axons will be used in the chimpanzee, although some autoradiographs will be done with this species. The cytoarchitecture of the red nucleus of the chimpanzee and human will be studied in Nissl stained sections. Quantitative cytological dyes will be employed and perikarya characterized as to amounts of RNA and DNA using a Zeiss Cytoscan System attached to a PDP-12 digital computer. These data will be compared with results obtained in previous studies with the rehesus monkey. The numbers of various types of perikarya and their areas also will be determined. The computer system also will be employed to evaluate retrograde cell changes in the brainstem of the chmimpanzee following lateral funiculotomy.